/*
 *  Copyright 2013 National Institute of Advanced Industrial Science and Technology
 *  
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *  
 *      http://www.apache.org/licenses/LICENSE-2.0
 *  
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.sss.common.io;

import java.util.HashMap;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.sss.mapreduce.SssException;
import org.sss.mapreduce.StorageNode;

public class StreamDBSet {
  private static Logger logger = LoggerFactory.getLogger(StreamDBSet.class);
  private final Map<StorageNode, StreamDB> dbMap = new HashMap<StorageNode, StreamDB>();
  private int nRef;

  public StreamDBSet() {
    this(false);
  }

  public StreamDBSet(boolean isNotUsedByMe) {
    this.nRef = isNotUsedByMe ? 0 : 1;
  }

  public synchronized StreamDB get(StorageNode node) throws SssException {
    assert nRef > 0: "referrence count is not positive.";

    StreamDB db = dbMap.get(node);
    if (db == null) {
      db = new StreamDB(node.getHostName(), node.getPort());
      dbMap.put(node, db);
    }
    return db;
  }

  public synchronized void incRef() {
    nRef++;
  }

  public synchronized void close() throws SssException {
    if (--nRef == 0) {
      for (StreamDB db: dbMap.values()) {
        db.close();
      }
      dbMap.clear();
      logger.debug("close db");
    }
  }
}
